1. Field of the Invention
This invention relates to new and useful improvements in tools for the drilling of oil and gas wells and more particularly to a float tool such as a float collar or float shoe.
2. Description of the Prior Art
In the History Of Oil Well Drilling, J. E. Brantley, pp. 1273-1279, there is a detailed description given of the origin and development of casing shoes and particularly float shoes and also the development of float collars. The first casing shoes were designed for driving pipe through tight spots and when it was being carried. Float shoes were developed for the purpose of taking the load off the hoist when lowering the drill into a well. The pipe was floated into the well making use of the hollow pipe construction and the drilling mud or other well drilling fluid which surrounds the pipe in the bore hole.
A float shoe is positioned on the bottom of a drill pipe which is being lowered into a well bore and has end portion which is rounded and is filled with cementitious material (cement or concrete). It has a longitudinal passage in which there is positioned a check valve. The check valve closes in an upward direction and opens in a downward direction. As a result, when the pipe is being lowered, the check valve is closed and the pipe is kept free of fluid, thus providing the buoyancy for floating the pipe into position. When the pipe has been lowered into position the cement which is used for cementing the well bore, can be introduced through the pipe and will pass downwardly through the check valve and out around the pipe and upwardly to fill the well bore around the pipe.
Float collars are sometimes used, either alone or together with a float shoe, for providing buoyancy. A float collar may be used to provide buoyancy while still allowing for connection to a drill bit. The float collar differs from a float shoe in that it has threaded connections on both ends for connection on one side to a drill pipe and on the other side to a drill collar or directly to a drill bit sub. These various features of construction are discussed at length in the cited portion of the History Of Oil Well Drilling.
Several patents are illustrative of the patent art on float collars and float shoes.
LeCocq U.S. Pat. No. 1,485,512 discloses a cemented well liner.
Baker U.S. Pat. No. 1,685,307 discloses a metal tubular cementing and floating shoe for use in drilling oil and gas wells. The type of shoe which is shown does not have the typical cemented plug in the end.
Baker U.S. Pat. No. 1,776,613 discloses a well shoe for floating a casing into place. The float shoe which is shown has a downwardly opening check valve which is cemented in place by the cement or concrete plug at the end of the shoe.
Baker U.S. Pat. No. 1,994,846 discloses a float shoe having a plug closure at the end which closes the opening through the shoe while the casing is being floated into the place. The plug may thereafter be forced out to permit the cementing of the well.
Harris U.S. Pat. No. 3,322,499 discloses a another type of float shoe having a check valve cemented in place.